1. Field of the Invention
The present invention relates to a suction canister, and more particularly, concerns a suction canister used for withdrawing and collecting body fluids from a patient during surgical procedures.
2. Description of the Prior Art
Suction canisters are employed in the hospital environment, and particularly during surgical procedures, to drain body liquids from a patient. In general, suction canisters employ a collection system and a vacuum source, such as a pump, to facilitate this drainage procedure. The canister generally includes a flexible line or hose connected to the vacuum source so that vacuum can be applied to the interior of the canister. Another flexible line or hose extends from the canister to the source of body liquids in the patient. Once the vacuum is applied, a negative pressure gradient is communicated through the interior of the suction canister so that body liquids are drawn into the canister.
As the suction canister fills, a need for controlling overflow has been recognized. To this end, a number of prior suction canister devices have employed shut-off valves to control any overflow of liquid from the canister. More particularly, previous devices have employed hydrophobic filters to prevent the passage of liquid out of the suction canister during operation. U.S. Pat. Nos. 3,719,197; 3,738,381; 4,013,076; 4,111,204 and 4,275,732 disclose suction canisters wherein the use of hydrophobic material is employed for liquid control purposes. U.S. Pat. Nos. 4,111,204 and 4,275,732 both use a hydrophobic material in conjunction with a filter bag disposed inside the suction canister.
In addition to the control of liquid overflow, suction canister systems have also been concerned with particulate matter control, including bacteria. U.S. Pat. No. 4,228,798, discloses a medical suction system with a hygroscopic filter sufficient to filter bacteria having dimensions less than about five microns from the airstream developed during the suctioning process. Other filter materials are known to remove bacteria and particulate matter from medical gases. For example, W. L. Gore and Associates, Inc., of Elkton, Md., makes filters known as GORE-TEX.RTM. membranes and laminates to vent air while preventing fluid leakage or bacterial entry. Descriptions of these membranes and laminates are found in three W. L. Gore and Associates, Inc. publications, entitled, "GORE-TEX Membrane Products" (1980); "GORE-TEX Expanded PTFE" (1978); and "GORE-TEX Expanded PTFE" (an ICI Engineering Plastics publication reprint, No. 4, 1975). U.S. Pat. No. 4,187,390 also describes some of these filter materials. The Applicants are also familiar with the particulars of U.S. Pat. Application Ser. No. 241,153, filed Mar. 6, 1981, now abandoned, and a continuation application thereof Ser. No. 494,745, filed May 16, 1983, the details of both applications of which are incorporated herein by reference, and which disclose a suction canister assembly using a unitary shut-off valve, filter element located within the interior of a rigid suction canister.
The use of surgical tools such as lasers and electric knives in surgical procedures is increasing. Both of these tools minimize bleeding by cauterizing while cutting tissue and both have a tendency to produce smoke which may sometimes be dense. This smoke creates problems for suction canisters using hydrophobic filters as valves since it has the ability to rapidly shut down the valve regardless of the amount of fluid collected in the canister. Therefore, it is necessary to filter out this smoke before it can reach the hydrophobic filter. It is also necessary to filter this smoke since it contains proteinized vapors which, if they get through the filter, can contaminate the apparatus and areas downstream from the filter by providing a growth media for bacteria.
While body liquid control and particulate matter filtration, including bacteria, have been addressed by the prior art in suction canister systems, the prior art has not addressed the problem of smoke filtration. There is still a need for a straightforward, easily fabricated system which can adequately filter smoke and other particulate matter including bacteria while controlling liquid overflow. In addition, it is also desirable that the mechanism for controlling liquid overflow also be capable of shutting down the vacuum system which draws liquid into the suction canister. It is to these ends that the present invention is directed.